Perturbation of analytic hermitian matrix functions
Israel Gohberg, Peter Lancaster, Leiba Rodman · Applicable Analysis · 1985
The behaviour of real eigenvalues of selfadjoint analytic matrix valued functions under small selfadjoint analytic perturbations is studied. Attention is paid mainly to the case when the perturbation is definite (or semidefi-nite). Earlier results of the authors concerning matrix polynomials of first degree are extended to the case of analytic functions.